The Fabrication Of Several Novel Electrochemical Sensors For Pesticides And Veterinary Residues

As the largest agricultural country in the world,the planting and animal husbandry of China have developed rapidly in recent years.In order to increase the yield and improve the quality of agricultural/husbandry products,pesticide/veterinary drugs are used more and more widely.However,it inevitably leads to a series of problems caused by pesticide/veterinary drug residues,which will cause pollution to the environment and great harm to human health.Therefore,it is necessary to strengthen the supervision and risk monitoring of agricultural/veterinary drugs.Compared to other analytical methods,electrochemical means is much more readily to operate,easies to be done in sites and with lower price.It shows great promise for the detection residues of pesticide/veterinary drugs.However,the conventional electrode can not meet the requirement of monitoring due to its poor selectivity and specificity,poor sensitivity and narrow linear range.Therefore,it is necessary to prepare novel electrochemical sensors.Based on this,two preparation routes of eletrochemical sensors for organophosphorus insecticides and quinolones were developed,three kinds of chemically modified electrodes（CMEs）were prepared.It is consisted of several parts as followed:（1）Fabrication of Zr（IV）-MDPA-Au via layer-by-layer self-assembly for the high selective detection of methyl parathionA simple method for the preparation of p-Nitrobenzene substituted organophosphorus pesticides electrochemical sensor with high selectivity is proposed via layer by layer self-assembly（Lb L）.Here,11-mercaptoundecyl phosphoric acid（MDPA）was selected and used as one bridge.The fabrication was done by utilizing the specific chelation between gold element and mercapto group in MDPA,and Zr（IV）ion and phosphate group in MDPA.By the way,Zr（IV）was readily immobilized on the surface of the Au electrode via Lb L,without chemically derivative step.The morphology and elements of the modified electrode were characterized by scanning electron microscopy（SEM）and energy-dispersive spectroscopy（EDS）,the results showed that Zr（IV）-MDPA-Au was successfully prepared.The Zr（IV）-MDPA-Au was applied to the determination of MP via square-wave voltammetry（SWV）.The linear range is 3.8 nmol/L～6.8×10² nmol/L（R²>0.99）,and the detection limit is as low as 0.84 nmol/L（S/N=3）.Moreover,this sensor shows high selectivity,good reproducibility and stability.Zr（IV）-MDPA-Au was successfully used to detect MP in the real water sample and high performance liquid chromatography（HPLC）was used to verify the feasibility and reliability of this method.（2）Preparation of norfloxacin-porous magnetic molecularly imprinted polymer electrochemical sensor.Firstly,porous magnetic molecularly imprinted polymers（m MIPs）were prepared in the method of oil-in-water emulsifier-free emulsion,and fixed to the surface of GCE by with nafion matrix.SEM and EDS show that m MIPs/GCE was successfully prepared.The m MIPs/GCE was applied to the determination of NFX via SWV.The linear range is0.05～3×10²μmol/L（R²>0.98）which is as wide as four orders of magnitude,and the detection limit is 15 nmol/L（S/N=3）.The detection of NFX is not affected by common interferences,and has good reproducibility and stability.It has been successfully used in the detection of NFX in complex rat plasma samples.HPLC verification experiments show that the method has high feasibility and accuracy.（3）Preparation of norfloxacin-molecularly imprinted polymerized electrochemical sensor by in-situ polymerization.A route was proposed for preparing molecularly imprinted polymer electrochemical sensor on GCE surface by in-situ polymerization.Firstly,a layer of amino group was derived from the surface of GCE,and a molecularly imprinted polymer membrane with NFX as template molecule was formed in-situ polymerization of aminated GCE.The morphologies and components of the coating were characterized by SEM and EDS,the results showed that MIPs-NH₂-GCE was successfully prepared.The MIPs-NH₂-GCE was applied to the determination of NFX via SWV.The linear range is 0.50μmol/L～1.0×10²μmol/L（R²>0.91）and the detection limit is 0.16μmol/L（S/N=3）.The detection of NFX is not affected by common interferences,and has good reproducibility and stability.Furthermore,it was successfully applied to the detection of NFX in real water samples,and the feasibility and accuracy of the method were verified by HPLC.